<template>
  <div class="spec-preview">
    <img :src="imgUrl || skuDefaultImg"/>
    <div class="event" @mousemove="moveMask"></div>

    <!-- 右侧大图区 -->
    <div ref="big" class="big" >
      <img :src="imgUrl || skuDefaultImg" :style="{left: -maskLeft * 2 + 'px', top: -maskTop * 2 + 'px'}"/>
    </div>
    <div :style="{left: maskLeft + 'px', top: maskTop + 'px'}" class="mask"></div>
  </div>
</template>

<script>
  export default {
    name: "Zoom",
    props: ['skuDefaultImg'],
    data(){
      return {
        maskLeft: 0,
        maskTop:0,
        imgUrl: ''
      }
    },
    
    methods: {
      moveMask(e){
        // let mouseX = e.clientX, mouseY = e.clientY
        // let {left: imgX, top: imgY} = e.target.getBoundingClientRect()
   
        // this.maskLeft = mouseX - imgX - 100
        // this.maskTop = mouseY - imgY - 100

        // this.maskLeft <= 0 && (this.maskLeft = 0)
        // this.maskTop <= 0 && (this.maskTop = 0)
        // this.maskLeft > 200 && (this.maskLeft = 200)
        // this.maskTop > 200 && (this.maskTop = 200)

        // this.$refs.big.scrollTop = this.maskTop * 2
        // this.$refs.big.scrollLeft= this.maskLeft * 2

        // this.maskLeft += 'px'
        // this.maskTop += 'px'

        //  ({offsetX: this.maskLeft,  offsetY: this.maskTop}) = e

        // 简单的写法
        let x = e.offsetX - 100, y = e.offsetY - 100
        x < 0 && (x = 0)
        y < 0 && (y = 0)
        x > 200 && (x = 200)
        y > 200 && (y = 200)
        this.maskLeft = x
        this.maskTop = y
      }
    },
    mounted(){
      // 自定义：选择图片的事件，
      this.$bus.$on('selectImg', imgUrl => {
        this.imgUrl = imgUrl
      })
    }
  }
</script>

<style lang="less">
  .spec-preview {
    position: relative;
    width: 400px;
    height: 400px;
    border: 1px solid #ccc;

    img {
      width: 100%;
      height: 100%;
    }

    .event {
      width: 100%;
      height: 100%;
      position: absolute;
      top: 0;
      left: 0;
      z-index: 998;
    }

    .mask {
      width: 50%;
      height: 50%;
      background-color: rgba(0, 255, 0, 0.3);
      position: absolute;
      left: 0;
      top: 0;
      display: none;
    }

    .big {
      width: 100%;
      height: 100%;
      position: absolute;
      top: -1px;
      left: 100%;
      border: 1px solid #aaa;
      overflow: hidden;
      z-index: 998;
      display: none;
      background: white;

      img {
        width: 200%;
        max-width: 200%;
        height: 200%;
        position: absolute;
        left: 0;
        top: 0;
      }
    }

    .event:hover~.mask,
    .event:hover~.big {
      display: block;
    }
  }
</style>